It is known to use ceramic paints to coat at least a portion of the surface of a glass sheet, to form an opaque border around the peripheral marginal surface thereof, for the preparation of an automotive vehicle windshield, sidelite, or backlite. Such a concealment band is applied to the inner surface of the glass sheet (the side of the glass sheet nearest the vehicle occupants) to protect the ceramic paint layer from the corrosive and erosive effects of the atmosphere exterior of the vehicle. The need to protect such a painted surface from the corrosive effects of atmospheric gases and vapors is particularly great where the ceramic paint contains a metal powder.
Metal powders are used extensively in modern ceramic paints due to their ability to prevent sticking of the paint to a forming die during a glass sheet press bending operation and their ability to prevent the formation of surface defects during a gas hearth glass sheet forming operation. Thus, virtually all modern motor vehicle glazings having a concealment band around the periphery thereof employ a ceramic paint layer on the interior surface of the glass.
U.S. Pat. Nos. 4,684,389 and 5,090,983, both to Boaz, disclose metal-containing ceramic paints useful for forming a concealment band on an automotive glazing. Such a concealment band is only applied to the interior surface of the glass sheet due to its susceptibility to the corrosive and erosive effects of the atmosphere exterior of the vehicle.
Modern styling changes have resulted in a desire to place concealment bands on the exterior surfaces of automotive glazings. Ceramic paints containing metal powders are superior to conventional ceramic paints, due to their ability to prevent sticking and defects during glass sheet forming operations. The use of metal containing ceramic paints results in increased glazing productivity and painted surface quality. However, the addition of metal powders also results in a particularly unsuitable exterior paint.
Organic paints, which provide superior durability and aesthetic quality, will not stick to a glass surface, and so likewise cannot be used to form a concealment band on the exterior surface of an automotive glazing.
It would be desirable to develop a process for painting at least a portion of the exterior surface of a glass sheet, which painted surface would be durable, resistant to atmospheric gases and vapors, and aesthetically pleasing.